U.S. Pat. No. 4,979,416 discloses a cutting link for a saw chain of a motor-driven chain saw which has forward and rearward running surfaces. In order to achieve a uniform cutting performance, the suggestion is made to form the rearward running surface of the cutting link larger than the forward running surface. The rearward running surface should be so dimensioned that the removal of material caused by wear is approximately the same at the elevation of the two running surfaces. The movability of the chain is considerably limited because of the lengthening of the rearward running surface. A saw chain of this kind is not suitable for use in guide bars having a small change-of-direction radius.
Saw chains having symmetrically configured forward and rearward surfaces have a short service life under heavy loads because the saw chain tears in the region of the trailing rivet opening. It has been shown that friction martensite forms under heavy loads at the rearward tooth foot which causes an embrittlement of the material. Because of the material embrittlement, tears result which extend up to the trailing rivet opening and lead to a break in the chain. Likewise, the greater load on the rearward running surface leads to an intense removal of material. This leads to a reduction of the wall thickness in the region of the trailing rivet opening and consequently to a break of the chain.